[srslte-users] RSRP/SINR issues with pdsch_ue

Sina Khanifar sina at rsrf.com
Wed May 10 17:33:37 UTC 2017


No, I'm using a Nuand bladeRF x40.
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On Wed, May 10, 2017 at 10:26 AM, Ismael Gomez <ismael.gomez@
softwareradiosystems.com> wrote:

> Are you using B200/B210?
>
> On Wed, 10 May 2017 at 19:13 Sina Khanifar <sina at rsrf.com> wrote:
>
>> Hi Ismael,
>>
>> Thanks for the reply.
>>
>> > That's because the frequency response of the RF frontend is not flat
>> throughout all the frequencies. That's why we use the RSSI on-chip sensor
>> to compute the rf_gain_offset automatically. Have you tried that?
>>
>> The pdsch_ue script doesn't have the rf_gain_offset variable, but I
>> switched over to testing with cell_measurement.c where that variable is
>> included. Unfortunately I'm seeing similar results.
>>
>> Here is a summary of results using cell_measurement: https://www.
>> dropbox.com/s/xxejcc0pc5u0zl3/srslte-measurements.png?dl=0
>>
>> As you can see, the RSRP varies from the handset measured values. For
>> consistency all the handsets I am testing with are from the same vendor.
>>
>> > The way SINR is computed is vendor-specific so it's difficult to
>> compare across devices. You can try looking at RSRQ and compare that value.
>> RSRQ is a standarized equivalent metric of the SINR.
>>
>> If you look at the screenshot in the Dropbox link, I was actually seeing
>> a similar inconsistency with the RSRQ values.
>>
>> Thanks again for the help,
>>
>> Sina.
>>
>> On Wed, May 10, 2017 at 4:55 AM, Ismael Gomez <
>> ismael.gomez at softwareradiosystems.com> wrote:
>>
>>> Hi Sina,
>>>
>>> On Tue, 9 May 2017 at 21:38 Sina Khanifar <sina at rsrf.com> wrote:
>>>
>>>> Similar to the recent thread around issues with the cell_measurement
>>>> thread, I'm seeing problems with the pdsch_ue example script. I've tried
>>>> changing the RSRP and SINR calculations to make them better match real UE
>>>> measurements. For example, I am currently using:
>>>>
>>>>
>>> rsrp = 12*log10(rsrp/rf_gain_offset) where rf_gain_offset is set via an
>>>> arg to 2e9
>>>> sinr = 20*log10(sinr/noise/5)
>>>>
>>>> I've experimented with various values here, but continue to have
>>>> issues. In particular:
>>>>
>>>> * The RSRP gain offset appears to vary both with frequency and the
>>>> carrier signal's bandwidth. srs-lte shows higher rsrp at higher
>>>> frequencies, and higher rsrp at higher bandwidths.
>>>>
>>>
>>> That's because the frequency response of the RF frontend is not flat
>>> throughout all the frequencies. That's why we use the RSSI on-chip sensor
>>> to compute the rf_gain_offset automatically. Have you tried that?
>>>
>>>
>>>> * The SINR in the default code is never negative, whereas it is often
>>>> negative as measured by test UEs. It also generally doesn't match up to the
>>>> UE measurements, hence my 20*log10(sinr/noise/5) adjustment. This
>>>> alternative equation is still not very accurate, but at least generates
>>>> some negative values.
>>>>
>>>
>>> The way SINR is computed is vendor-specific so it's difficult to compare
>>> across devices. You can try looking at RSRQ and compare that value. RSRQ is
>>> a standarized equivalent metric of the SINR.
>>>
>>>
>>>>
>>>> Any thoughts on what might be causing these two issues?
>>>>
>>>> Thanks.
>>>>>>>> _______________________________________________
>>>> srslte-users mailing list
>>>> srslte-users at lists.softwareradiosystems.com
>>>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
>>>>
>>>
>>>>
>
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